I know that soft copper pre-made linesets are typically used between the outdoor unit and air handler, but I would like to use rigid tubing to go from the 2nd floor air handler down and interior wall and run over to the outdoor unit in the basement.

The air handler isn't installed, but I would like to get the pipe in the wall so I can close up the wall.

Most of the soft copper up to 1/2" OD sold at the hardware stores is ACR. 5/8 and 7/8 OD would be 1/2 and 3/4 type L.

The important thing about ACR is that it is cleaned internally. If you wanted to use type L hard, some serious flushing would be required before connecting to the equipment. I would get input from a good HVAC contractor about the feasibity of this.

Brazing is the preferred way, less expensive and easier and you must have a nitrogen supply flowing through the pipe while doing it to prevent oxidation... anything foreign left in the line like flux or oxidation flakes can / may cause problems such as failure with the compressor.

I did some research on the brazing with nitrogen. Looks like many out techs in the residential HVAC industry skip the "niitrogen" in the lines when brazing.

What I read is that there is minimal brazing joints and minimal oxidation in the residential lines, and also if you use a filter before the air handler you sorta cover your self?

I do not plan on doing many joints, if any. My plan to run the 2 lines down from the second floor to the basement so then the connections can be extended at the 2nd floor and basement to the units. I have the coiled lineset, but would rather not try and snake this down the wall cavity.

The airhandler and outdoor units will be installed at the end of the season.

If you really, REALLY want the hard temper tubing in the wall I strongly suggest that you get the installer you are going to use for the rest of the system to install the hard temper tubing. Otherwise, when it comes time for the rest of the installation you won't have any guarantee on the lines in the wall. Probably no guarantee on the system either.

ACR tubing is called out by OD. Type K,L,M hard tube ( what everyone calls copper pipe) is called out by trade size, which is approximate ID, and the OD is always EXACTLY 1/8 larger than the called out ID. For example, 1/2" tube is approximately 1/2" ID, but the exact ID varies with wall thickness, depending on whether it is K, L, or M. BUT IN ALL CASES, the OD is EXACTLY 5/8"

We use rigid tubing mostly in commercial jobs. For AC use I prefer soft copper because you don't have as many joints and you have less fittings. The more fittings the more resistance, and the greater chance of leaks/contamination.

You must braze the joints and all manufacturers require you to do a dry nitrogen purge while brazing to prevent oxides from forming on the interior of the tubing. If you have a failure due to a bunch of oxide crud clogging the TXV they will not honor the warranty. A lot of guys don't do it and everything works fine but it is the proper way to do it.

After you finish brazing all your joints you need to pull a deep vacuum (under 100 microns) to check for leaks and remove any moisture.

Moisture is another problem using rigid lengths of lineset. It must be sealed and dehydrated from the factory or it will have crud and air which contains moisture inside.

If your system will be using R410-A you will really have to be careful about moisture. The oil used with it loves moisture it soaks it up right from the air.

I recommend you use soft copper, don't remove the rubber plugs just run the lineset and then hire an HVACR tech to braze the joints and charge the system. That way you don't have to spend thousands on tools you will use once. You will also know it is done right for the warranty sake.

The hardest part is not tearing the insulation off the suction line when going through floor/ceiling penetrations. Second hard part is not to kink the suction line. 7/8 is a pain not to kink, just be gentle and take your time.

You might need a tubing bender if you are not expierenced with the larger sizes of soft copper.

Thanks for the advice, I'm going to crack open the lineset tomorrow and do a test "uncoiling" to see how it behaves. If I think I'm not able to get a decent amount unrolled into a straight section I'll borrow/buy a tubing bender.